Quantifying the relationship between the plasmapause and the inner boundary of small-scale field-aligned currents, as deduced from Swarm observations

Abstract

Abstract. This paper presents a statistical study of the equatorward boundary of small-scale field-aligned currents (SSFACs) and investigates the relation between this boundary and the plasmapause (PP). The PP data used for validation were derived from in situ electron density observations of NASA's Van Allen Probes. We confirmed the findings of a previous study by the same authors obtained from the observations of the CHAMP satellite SSFAC and the NASA IMAGE satellite PP detections, namely that the two boundaries respond similarly to changes in geomagnetic activity, and they are closely located in the near midnight MLT sector, suggesting a dynamic linkage. Dayside PP correlates with the delayed time history of the SSFAC boundary. We interpreted this behaviour as a direct consequence of co-rotation: the new PP, formed on the night side, propagates to the dayside by rotating with Earth. This finding paves the way toward an efficient PP monitoring tool based on an SSFAC index derived from vector magnetic field observations at low-Earth orbit. Keywords. Magnetospheric physics (plasmasphere)

On some features characterizing the plasmasphere–magnetosphere–ionosphere system during the geomagnetic storm of 27 May 2017

“…A definite estimation of the magnitude of the erosion was not possible due to the lack of data in the morning sector and in general at low latitudes, although an upper limit of 3 R E for the plasmapause position can be deduced from the post-noon radial density profile of 28 May 2017. An analysis of observations from Swarm satellites (Friis-Christensen et al 2006), using the technique by Heilig and Lühr (2018), also indicates a midnight location of the plasmapause at L ~ 2.5 at the beginning of 28 May 2017 (not shown).…”

Storm Time EMIC Waves Observed by Swarm and Van Allen Probe Satellites

“…Red vertical dashed lines represent the EMIC wave period. Black dashed line denotes the plasmapause location by adopting the same method of Heilig and Lühr (). MLT = magnetic local time; ILat = invariant latitude; UT = universal time; VAP = Van Allen Probe; EMIC = electromagnetic ion cyclotron.…”

“…As an example, Figure shows EMIC wave events and the corresponding spectra of H + , He + , and O + recovered by the Helium, Oxygen, Proton, and Electron Mass Spectrometer, as well as the electron density measured by the VAP Electric Fields and Waves instrument between 15:00 and 16:00 UT in the afternoon sector on 23 June. The black vertical dashed line in the bottom panel indicates the location of the plasmapause identified by adopting the method used in Heilig and Lühr (), that is, a factor of 5 drop or more over an L range of less than 0.25 R E . This gradient threshold (Heilig & Lühr, ) is about twice as large as those applied by previous studies (He et al, ).…”

“…The black vertical dashed line in the bottom panel indicates the location of the plasmapause identified by adopting the method used in Heilig and Lühr (), that is, a factor of 5 drop or more over an L range of less than 0.25 R E . This gradient threshold (Heilig & Lühr, ) is about twice as large as those applied by previous studies (He et al, ). The first EMIC wave was generated close to the plasmapause but slightly outside, where low‐ and high‐energy ions coexisted, which indicated that the EMIC wave was generated when the ring current and plasmasphere or plasma plume particles overlapped.…”

Plasmasphere and topside ionosphere reconstruction using METOP satellite data during geomagnetic storms

“…This dayside ionospheric filling in the presence of the Earth's rotation produces a quite large torus of cold plasma, which becomes quite disturbed during active geomagnetic conditions. Numerous studies have analyzed the disturbed plasmasphere with particular interest in the internal dynamics (Singh et al, 2011), boundaries (Verbanac et al, 2015;Heilig and Lühr, 2018), erosion by enhanced magnetospheric convection (Carpenter, 1970;Zhelavskaya et al, 2017) and coupling processes with the magnetosphere (Borovsky and Valdivia, 2018) and ionosphere (Pierrard and Voiculescu, 2011).…”